Pharmaceutical preparations that have been so far used for percutaneous administration of medicaments have dosage forms of ointment, gel, lotion, and the like. Recently, however, a patch, which is also called a tape-aid (patch) or a gel patch (cataplasm), has been practically used and noted, because it can quantitatively administer medicaments and can be peeled off at any time when it has induced any side effects. Such a patch includes a local preparation containing a non-steroidal drug aimed at anti-inflammatory analgesic effects or a systemic preparation containing a nitric acid ester aimed at remedying circulatory diseases or containing a female hormone aimed at remedying climacteric disturbance or osteoporosis.
On the other hand, there have arisen such a problem that, when these patches are applied, ultraviolet rays from the sun decompose the drug contained in the base thereof to lower the content and thus does not allow the drug to exhibit its original efficacy and another problem that the photolyzed products induce an allergy to bring about adverse effects.
For inhibiting the influence of the ultraviolet light of the sun, Japanese Pat. Publn. No. Hei 5-8169 (No.8169/1993) discloses an external preparation in which an effective ingredient is prevented from photolysis by incorporated with an ultraviolet absorbent in the base of the preparation. Further, Japanese Pat. Appln. Laid-Open Gazette No. Hei 10-265371 (No.256371/1998) discloses a percutaneously absorbable patch having as a backing a laminate composed of two or more layers, in which at least one layer of said laminate is a resin film containing an ultraviolet absorbent.
As described above, the means for keeping the stability of a medicine in patches has generally been to incorporate an ultraviolet absorbent into the base, but there has remained a problem to be worried about as to safety and the like due to said absorbent's direct contact with or absorption into the skin. On the other hand, the patch whose backing, which will be directly exposed to the ultraviolet rays of sun, is made of a laminate comprising two or more layers for screening the ultraviolet requires troublesome manufacturing steps for laminating the backing and also involves high costs.
The present invention has been made for solving the above problems, and an object thereof is to provide a patch excellent in securing therapeutic effects and in safety for the skin by improving the photostability of a medicine with a backing composed of a single layer.